Opera was king, but I just can't live without Firebug in Firefox. Opera has its own as well but I just couldn't get into it. I have slowly been using Firefox more and more. Plus, my schools web based classes are made for IE, don't work in Opera, but work fine (with some minor rendering issues) in Firefox. Frankly, Opera was my favorite due to the tabbed browsers and fast loading...now that Firefox has the tabs and they work great....Opera has been getting used less and less.

For web development Firefox is King, or, well, when you do office web development, IE is King. MS uses so many ActiveX components that only they support that all others are unusable.

So I use IE for work and Opera for private browsing. When I take on open source assignments I use Firefox, since Firebug is so d**n good. I agree with Strolen on his assessment of Firebug vs. Opera's tools.

Firefox is much more stable though. I hate using Opera in my online banking, as the JVM support for Opera seems buggy at best.

Opera 10.5 has critically failed every time I load it. Can't get it to work at all. Sucks up 100% CPU and the bogs me down. Tried all variations of reinstall/repair etc to no effect. Firefox has been taking over my heart for a long time. Latest version with the single click theme update is just neat, its continued support of many CSS3 toys. Firebug is priceless to me and, for that alone, Firefox has finally won me over I fear. I patiently await 10.x and will try again but, alas, Opera is no longer loaded on my system.

I tried to like Firefox 4...and I do, Chrome just does things more intuitively. I don't like the hidden tabs when I have a thousand open, I like Chrome holding a TON more tabs without the scrolling. Firefox has also frozen me a couple 3 times already for apparently no reason.

Next I will try the latest Opera. I have abandoned it for the past 6+ months since I got a corrupted install or something and couldn't get it loaded. Have Windows 7 now, time to try again.